#ifndef DOUBLE_LIST /* this string SHOULD NOT previously exist */ #define DOUBLE_LIST

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Paulina Whitehead
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1 /* This is a personal header file. Call it double_list.h * Its name should be reflected into the macro definition (#define). * For instance, here I should say something like: * #define DOUBLE_LIST #ifndef DOUBLE_LIST /* this string SHOULD NOT previously exist #define DOUBLE_LIST typedef struct Persoana char Nume[16]; struct Persoana *pnext; struct Persoana *pprec; PERS, *ppers, **pppers; typedef enum BFalse, True BOOL; /* Note: BOOL!= unsigned int /* Insertion and deletion functions /* If required to initialize each node's data (information fields) * then as last function argument I should have an entire structure void ins_node2(pppers, ppers, char*); void del_node2(pppers, ppers); /* vlad: compute the list's length inside each of these fcts void parcurg2_lr(ppers, unsigned int*, pppers); void parcurg2_rl(ppers, unsigned int*, pppers); /* check that the list is empty BOOL isempty(ppers); #endif 1

2 /* Another module in the project (double_list.c) * This one contains the implementation of the personal functions. #include "double_list.h" /* should be placed within the same folder * as the other modules belonging to this project #include <stdio.h> #include <stdlib.h> #include <assert.h> #include <string.h> /* vlad: the functions personal implementation void ins_node2(pppers ppprim, ppers p, char *Nume) ppers q = (ppers)malloc(sizeof(pers)); assert(q!= NULL); strcpy(q->nume, Nume); /* vlad: update the information fields, * once for any insert if(p == NULL) /* vlad: insert new node as the 1st node (mandatory: 'prim' reference changes) q->pnext = *ppprim; q->pprec = NULL; if( *ppprim ) (*ppprim)->pprec = q; /* typical for double-linked lists *ppprim = q; else /* insert in the list AFTER node p (as for simply linked lists) q->pnext = p->pnext; q->pprec = p; if(p->pnext) p->pnext->pprec = q; /* vlad: save the current link p->pnext = q; /* vlad: update the new link; the old link vanishes void del_node2(pppers ppprim, ppers p) ppers q /*, prec, urm; /* vlad: here, p is the preceding node * and NOT the one about to be * deleted! /* vlad: in the first place deal with the links... if(p == NULL) q = *ppprim; /* vlad: retain the address of the first node: * this will be deleted if( (*ppprim)->pnext ) (*ppprim)->pnext->pprec = NULL;/* the former second node won't have * any previous node anymore *ppprim = (*ppprim)->pnext; /* vlad: 'by-pass' the first node 2

3 else q = p->pnext; /* the node about to be deleted if(p->pnext) p->pnext->pprec = p; p->pnext = q->pnext; #if 0 /* This alternate approach uses some helpful notations. * It is perfectly valid prec = q->pprec; urm = q->pnext; /* useful variables prec->pnext = urm; /* by-pass node q: forward link urm->pprec = prec; /* by-pass node q: backward link #endif /*... and finally delete the node free(q); /* vlad: left-to-right traversal void parcurg2_lr(ppers pstart, unsigned int *plen, pppers ppultim) assert(pstart!= NULL); ppers ref = pstart; *plen = 0; /* length is a sum-kind variable /* vlad: just in case. * Shouldn't traverse an empty list (forbidden!) do puts(ref->nume); /* data processing (*plen)++; /* list's length is computed *ppultim = ref; /* vlad: the last one points to the very last node ref = ref->pnext; /* go 'forward' (advance in the list) while(ref!= NULL); /* vlad: stop condition /* vlad: right-to-left traversal void parcurg2_rl(ppers pstart, unsigned int *plen, pppers ppprim) assert(pstart!= NULL); /* vlad: just in case. * Shouldn't traverse an empty list (forbidden!) ppers ref = pstart; /* vlad: from outside, the pstart should now point * to the LAST node(!) *plen = 0; do puts(ref->nume); /* data processing of each node (here it is minimal) (*plen)++; /* compute the list's length *ppprim = ref; /* vlad: at the last pass I retain 1 st node's address ref = ref->pprec; /* go 'backward' while(ref!= NULL); /* vlad: the 1 st node's prev link is NULL BOOL isempty(ppers prim) return (prim == NULL)? True : False;

4 /* The module file containing the main() function. Its name is main.c * The presence of this file gives this project the ability to run. * It contains calls to personal functions (the double-linked list's API). #include "double_list.h" /* should be placed within the same folder * as the other modules belonging to this project #include <stdio.h> #include <stdlib.h> #include <assert.h> #include <string.h> int main() unsigned int dim = 0; ppers prim = NULL; /* vlad: right now the list is empty (!) ppers ultim = NULL; /* vlad: here I will store the address * of the last node in the list. ppers prim_addr_computed = NULL; /* I won't use the (same) variable 'prim'. * I keep 'prim' for the 1 st node's address, and * 'prim_addr_computed' for the 1 st node * address, computed after the list traversal. /* vlad: create list. For instance 4 nodes. * The insertion takes place in several positions. fprintf(stdout,"create the list...\n"); ins_node2(&prim, NULL, "N1"); fprintf(stdout,"inserted 1st node... OK\n"); ins_node2(&prim, prim->pnext, "N2"); fprintf(stdout,"inserted another node... OK\n"); ins_node2(&prim, prim->pnext->pnext, "N3"); fprintf(stdout,"inserted another node... OK\n"); ins_node2(&prim, NULL, "N4"); fprintf(stdout,"inserted another node as the 1 st one... OK\n"); /* vlad: pass through the list fprintf(stdout,"scan through the list...\n"); parcurg2_lr(prim, &dim, &ultim); /* vlad: forward traversal fprintf(stdout,"done passing through the list (L-R). Computed dim: %u\n", dim); fprintf(stdout, "Last node's address (from traversal): %p\n", ultim); parcurg2_rl(ultim, &dim, &prim_addr_computed); /* backward traversal fprintf(stdout,"done passing through the list (R-L). Computed dim: %u\n", dim); fprintf(stdout, "1st node's address (from traversal): %p\n", prim_addr_computed); 4

5 /* vlad: delete the list (list's clean-up) fputs("now delete the list...\n", stdout); do /* the loop here can be a for(), as well. * Please give the equivalence using for() del_node2(&prim, NULL); while(!isempty(prim)); fputs("done deleting the list.\n", stdout); /* Double-check the correctness of the previous deletion operation fprintf(stdout, "Is the list empty now? %s\n", isempty(prim)? "Yes":"No"); fprintf(stdout, "Double-check: the prim pointer has the value: %p\n", prim); /* should be NULL fprintf(stdout, "All done!\n"); return 0;

#include <stdio.h> int main() { char s[] = Hsjodi, p; for (p = s + 5; p >= s; p--) --p; puts(s); return 0;

#include <stdio.h> int main() { char s[] = Hsjodi, *p; for (p = s + 5; p >= s; p--) --*p; puts(s); return 0; 1. Short answer questions: (a) Compare the typical contents of a module s header file to the contents of a module s implementation file. Which of these files defines the interface between a module and